v0.1.1: Add generic Reflector

Copy of notes from reflector.ts:

Implementation of a Kubernetes List/Watch client which furnishes a view of the watched data.
This is commonly called a 'Reflector' among the client libraries, though this one is less standard.

The core class here is a bit generic and tries to depend mostly on things within this file.
This is because a Reflector works pretty directly with Kubernetes API objects,
while this overall kubernetes_client module only serves as an API access path.
So you'll be furnishing your exact API structures by instiantiating the Reflector class.
(Usually the API will be from /x/kubernetes_apis/builtin/meta@v1/struct.ts but it can vary)

This class/file work fine, but the types and APIs are still unstable while I figure out
what's necesary for various usecases.
Please file issues or start discussions if you have any input!

The new module is not imported anywhere, it is a standalone addition. This will likely remain so until I"m more confident in the API.

Also, added contentType to the request options contract. This will be used for patching.